1. Field of the Invention
This invention relates to a three-dimensional electroformed shell for a mold and a process for manufacturing the same. The shell can be used for a variety of kinds of molds including a mold for making paper from pulp fiber, a mold for blowing a fibrous or granular material, a mold for foaming beads of polystyrene, polypropylene, or modified polyphenylene ether, a screen mold for preforming glass fiber, and a mold for making a molded resin product by vacuum, blow, stamping, injection, RIM urethane, or compression molding.
2. Description of Related Art
A three-dimensional electroformed shell having a multiplicity of apertures is used for a mold for making paper from pulp fiber. The apertures usually occupy about 1 to 50% by area of the surface of the shell. A number of methods have hitherto been employed for manufacturing such a shell, as summarized below.
(1) A punched metal plate having a multiplicity of apertures is pressed into a three-dimensional shape. It has, however, been impossible to form a punched metal plate into a complicated three-dimensional shape because of its poor press formability. Moreover, the use of an expensive press tool has resulted in an expensive product.
(2) A punched metal plate is bent, cut and welded into a three-dimensional shape. This method has, however, been able to make only a product of low dimensional accuracy. Moreover, the necessity of a great deal of time and labor has resulted in an expensive product.
(3) A three-dimensional shell having a small wall thickness is cast from e.g. an aluminum alloy, and apertures are drilled in the shell. The shell has however, been low in dimensional accuracy because of e.g. the warpage of its wall having a small thickness. Moreover, the necessity of a great deal of time and labor for drilling a multiplicity of apertures has resulted in an expensive product. It has even been difficult to drill the apertures in some portion or portions of the shell if it has a complicated shape.